Issue 49

C. Bellini et alii, Frattura ed Integrità Strutturale, 49 (2019) 791-799; DOI: 10.3221/IGF-ESIS.49.70 796 by increasing maximum and minimum strain, moving from A to B point. Therefore, in this section, the punch stroke required to reach the necking condition increases. In the B-D section, the maximum strain tends to decrease while the minimum strain increases, producing a situation in which the punch stroke increases until it reaches a maximum point (point C) and then it decreases to point D. Figure 5 : Achievement of the condition FLP = 1 adopting a value of the friction coefficient equal to 0, 0.05 and 0.1, respectively. Figure 6 : Photo of the specimen where the distance between the fracture line and the sheet centre is showed. Figure 7 : Punch stroke as a function of the friction coefficient.